1. Field of the Invention
The present invention relates to a magneto-optical recording medium capable of recording and reproduction of information with a laser beam using a magneto-optical effect and a method of reproducing information using this recording medium.
2. Related Background Art
In recent years, along with the development of the computer and processing techniques for processing a large volume of information, a high-density, large-capacity memory is required. One of the most promising media is a magneto-optical memory.
In a magneto-optical recording scheme, a laser beam irradiates a magnetic film having a perpendicular magnetic anisotropy to locally increase the temperature of the magnetic film, thereby reducing the coercive force of the heated film portion. At the same time, a recording magnetic field is applied in a direction opposite to the direction of initial magnetization, thereby performing magnetization reversal.
In this case, the linear recording density is defined by the laser wavelength .lambda. of a reproduction optical system and the numerical aperture (N.A.) of an objective lens.
That is, the pit period which defines the detection limit is given as f=.lambda./2.multidot.N.A.
In a conventional reproducing method, when a plurality of recorded pits are present within a laser spot, signals interfere with each other in a reproduction mode, and correct data cannot be reproduced.
To obtain a higher density, the laser wavelength .lambda. of the reproduction optical system must be shortened, and the numerical aperture N.A. of the objective lens must be increased.
However, the laser wavelength .lambda. of the reproduction optical system and the numeral aperture N.A. of the objective lens have limitations. Therefore, it is difficult to increase the recording density.